Get-Your-Life-Together Day

Organize your backpack and notebook - throw out anything that you don’t need

Be sure that you are missing NO assignments!

Make up any missing quizzes or tests (short answer for Cell Division?)

Get ahead - work on vocabulary for next unit / guided notes

Do work for another class (ONLY if you are completely caught up and ahead in HERE!

Read - it’s good for you.

Heredity:

Table of Contents

Introduction

Meiosis

Independent Practice-Meiosis

Mendelian Genetics

Non-Mendelian Genetics

Pedigrees

Independent Practice-Pedigrees

Unit 8: Heredity

Part I: Meiosis

Objectives: H.B.4C.2 Analyze data on the variation of traits among individual organisms within a population to explain the patterns in the data in the context of transmission of genetic information.

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Introduction

Heredity: the passing of genetic traits from parent to offspring

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Is genetic diversity a good thing?

Introduction

The beginning--Meiosis

The process of meiosis is essential to sexual reproduction just as mitosis is to asexual reproduction

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Sexual reproduction requires the fusion of gametes or sex cells (fertilization).

• Example: Sperm in human males, Egg in human females

Meiosis

In order for the offspring produced from sexual reproduction to have cells that are diploid (containing two sets of chromosomes, one set from each parent), the egg and sperm cells (gametes) must be haploid (contain only one of each type of chromosome).

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The cellular division resulting in a reduction in chromosome number is called meiosis.

Meiosis

Meiosis occurs in two steps:

1. Meiosis I, in which the homologous chromosome pairs separate, results in two haploid daughter cells with duplicated chromosomes different from the sets in the original diploid cell.
2. Meiosis II, in which the duplicated chromosomes from Meiosis I separate, resulting in four haploid daughter cells called gametes, or sex cells (eggs and sperm), with single (unduplicated) chromosomes.

Meiosis

It is important to keep in mind this key terminology when discussing Meiosis - chromosomes vs. chromatid.

Interphase precedes Meiosis I. (same things happen in interphase as did in Mitosis)

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Prophase I

• The nuclear membrane breaks down during Prophase I.
• The duplicated chromosomes condense and homologous chromosomes pair up. A homologous chromosome pair consists of two chromosomes containing the same type of genes. One chromosome in the pair is contributed by the organism’s male parent, the other chromosome in the pair is contributed by the organism’s female parent.

Meiosis

Prophase I

• As in mitosis, each duplicated chromosome consists of two identical sister chromatids attached at a point called the centromere.

Meiosis

Prophase I

• Because the homologous chromosome pairs very close to one another, an exchange of chromosome genetic material between pairs occurs in a process called crossing over.
• Crossing over causes the daughter cells to have different gene combinations from the original parent cell.

Meiosis

Metaphase I

• The paired homologous chromosomes are aligned along the equator of the cell with one chromosome of a pair on one side and one chromosome of a pair on the other side.
• Each pair is randomly oriented in terms of whether the paternal or maternal chromosome is on a given side of the equator.
• The result is that 23 chromosomes, some from the mother and some from the father, are lined up on each side of the equator. This arrangement is called independent assortment and also causes the daughter cells to have DNA that is different from the original parent cell.

Meiosis

Anaphase I

• The homologous chromosome pairs separate and move to opposite poles of the cell.
• Each daughter cell will receive only one chromosome from each homologous chromosome pair.
• Sister chromatids remain attached to each other.

Meiosis

Telophase I/Cytokinesis

• Chromosomes gather at the poles and cytokinesis begins.
• Cytokinesis occurs at the end of telophase I; the chromosomes uncoil and the nuclear membrane reforms
• Each of the two daughter cells at the end of meiosis I contain only one chromosome (consisting of two sister chromatids) from each parental pair, and are therefore haploid.
• Each daughter cell from meiosis I undergoes meiosis II

Meiosis

Interphase DOES NOT HAPPEN AGAIN as the cell moves into Meiosis II.

Prophase II

• The nuclear membrane breaks down.

Metaphase II

• Chromosomes, made up of two sister chromatids, line up across the center of the cell.

Anaphase II

• The chromosomes separate so that one chromatid from each chromosome goes to each pole.

Telophase II & Cytokinesis

• The nuclear membrane reforms around each set of chromosomes.
• The cell undergoes cytokinesis.
• The four resulting daughter cells are still haploid (as they were at the end of meiosis I) because meiosis II is almost identical to mitosis.

Meiosis

Meiosis

The DNA of the daughter cells produced by meiosis is different from that of the parent cells due to three sources of genetic diversity provided by sexual reproduction and meiosis:

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1. Fertilization combines the genetic material of two genetically unique individuals (the two parents)

2. Crossing-over produces new combinations of genes. (Prophase I)

3. Independent assortment allows for the possibility of about 8 million different combinations of chromosome.

Meiosis

Use the image to explain what happens during crossing over.

Type your response here

Give 2 ways that meiosis creates daughter cells that are different from parent cells.

Type your response here

Independent Practice-Meiosis

• Involves a reduction in the number of chromosomes
• Involves Interphase, Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis
• Crossing over occurs
• Part of sexual reproduction
• Daughter cells are 2N
• Produces gametes
• Tetrads are formed
• Daughter cells are haploid
• Part of asexual reproduction
• Involves Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis, Prophase II, Metaphase II, Anaphase II, Telophase II, and Cytokinesis
• Chromosome number of each daughter cell is the same as the parent cell
• Daughter cells are N
• Occurs in prokaryotic organisms
• Daughter cells are diploid
• Leads to greater genetic diversity in offspring
• Leads to less genetic diversity in offspring

Directions: Use the word bank provided below to compare and contrast Mitosis and Meiosis. Copy and paste the statements into the appropriate spot.

Independent Practice-Meiosis

MEIOSIS

MITOSIS

BOTH

Independent Practice-Meiosis

• Involves a reduction in the number of chromosomes
• Crossing over occurs
• Part of sexual reproduction
• Produces gametes
• Tetrads are formed
• Daughter cells are haploid
• Involves Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis, Prophase II, Metaphase II, Anaphase II, Telophase II, and Cytokinesis
• Daughter cells are N
• Leads to greater genetic diversity in offspring

• Involves Interphase, Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis
• Daughter cells are 2N
• Part of asexual reproduction
• Chromosome number of each daughter cell is the same as the parent cell
• Occurs in prokaryotic organisms
• Daughter cells are diploid
• Leads to less genetic diversity in offspring

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MEIOSIS

MITOSIS

BOTH

Independent Practice-Meiosis

Directions: Use the images provided below. Fill out the following slides by pasting the correct picture to the correct slide.

Independent Practice-Meiosis

Directions: Use the descriptions provided below. Fill out the following slides by pasting the correct description to the correct slide.

Homologous (matching) chromosomes form tetrads and may exchange genetic material through crossing over

The spindle forms and the tetrads attach to the spindle in the middle of the cell.

The sister chromatids separate and begin moving to opposite poles of the cell.

The chromosomes coil and the nuclear membrane disappears

The homologous chromosomes separate but the sister chromatids stay together.

The spindle forms and the pairs of chromatids line up in the middle of the cell

The chromatids move to teach corner of the cell and the cytoplasm begins to divide, resulting in 4 haploid sex cells.

The chromosomes move to the poles of the cell and the cell begins to divide.

Independent Practice-Meiosis

PROPHASE 1

Independent Practice-Meiosis

Homologous (matching) chromosomes form tetrads and may exchange genetic material through crossing over

METAPHASE 1

Independent Practice-Meiosis

The spindle forms and the tetrads attach to the spindle in the middle of the cell.

ANAPHASE 1

Independent Practice-Meiosis

The homologous chromosomes separate but the sister chromatids stay together.

TELOPHASE 1 / CYTOKINESIS 1

Independent Practice-Meiosis

The chromosomes move to the poles of the cell and the cell begins to divide.

PROPHASE II

Independent Practice-Meiosis

The chromosomes coil and the nuclear membrane disappears

METAPHASE II

Independent Practice-Meiosis

The spindle forms and the pairs of chromatids line up in the middle of the cell

ANAPHASE II

Independent Practice-Meiosis

The sister chromatids separate and begin moving to opposite poles of the cell.

TELOPHASE II / CYTOKINESIS II

Independent Practice-Meiosis

The chromatids move to teach corner of the cell and the cytoplasm begins to divide, resulting in 4 haploid sex cells.

Independent Practice-Meiosis

Independent Practice-Meiosis

POP QUIZ!

1. ​

2.

3.

4.

5.

6.

7.

8.

9.

10.

Directions: On a piece of paper, label numbers 1-10; use the following word bank to pick the correct stage of Meiosis for each image.

WORD BANK:

• Prophase I
• Metaphase I
• Anaphase I
• Telophase I
• Cytokinesis I
• Prophase II
• Metaphase II
• Anaphase II
• Telophase II
• Cytokinesis II

Unit 8: Heredity

Part II: Simple, Mendelian Genetics

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Objectives: H.B.4C.2 Analyze data on the variation of traits among individual organisms within a population to explain the patterns in the data in the context of transmission of genetic information.

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Allele- alternate version of a gene

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Dominant allele – expressed in the heterozygote

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Recessive allele – not expressed in the heterozygote

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Homozygote – pair of identical alleles for a character

Homozygous dominant- BB

Homozygous recessive - bb

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Heterozygote – two different alleles for a character (Bb)

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Genotype – genetic makeup

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Phenotype – appearance of an organism

IMPORTANT VOCABULARY:

Mendelian Genetics

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Gregor Mendel is known as the “Father of Genetics;” He was the first person to describe the manner in which traits are passed on from one generation to the next (and sometimes skip generations). Through his breeding experiments with pea plants, Mendel established three principles of inheritance that described the transmission of genetic traits before genes were even discovered. Mendel's insights greatly expanded scientists' understanding of genetic inheritance, and they also led to the development of new experimental methods.

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Mendelian Genetics

Genes come in different varieties, called alleles. Somatic cells contain two alleles for every gene, with one allele provided by each parent of an organism (Law of Segregation).

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One of Mendel’s principles states that it is impossible to determine which two alleles of a gene are present within an organism's chromosomes based solely on the outward appearance of that organism.

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An organism's genotype (two alleles) cannot be inferred by simply observing its phenotype (physical appearance).

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Mendel's experiments revealed that phenotypes could be hidden in one generation, only to reemerge in subsequent generations.

Parent 1: T /Tall

Parent 2: t / short

Offspring: Tt /Tall

Mendelian Genetics

Directions: Label the following as a phenotype (P) or genotype (G).

Red hair

Bb

hh

Green eyes

AA

Yellow seeds

Mendelian Genetics

Parent 1: T /Tall

Parent 2: t / short

Offspring: Tt /Tall

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How do hidden genes pass from one generation to the next?

• Although an individual gene may code for a specific physical trait, that gene can exist in different forms, or alleles (1 from each parent).
• In some cases, both parents provide the same allele of a given gene, and the offspring is referred to as homozygous.
• In other cases, each parent provides a different allele of a given gene, and the offspring is referred to as heterozygous for that allele.

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Mendelian Genetics

Directions: Label the following as a homozygous (HO) or heterozygous (HE).

Rr

Bb

hh

Aa

AA

rr

Mendelian Genetics

Parent 1: T /Tall

Parent 2: t / short

Offspring: Tt /Tall

Alleles produce phenotypes (or physical versions of a trait) that are either dominant or recessive.

1. The dominance or recessivity associated with a particular allele is the result of masking, by which a dominant phenotype hides a recessive phenotype.
2. In heterozygous offspring only the dominant phenotype will be apparent.

Mendelian Genetics

Directions: Label the phenotype of the following given the information: R (round seeds) is dominant to r (wrinkled seeds); A (no albinism) to a (albinism)

Rr

RR

aa

Aa

AA

rr

Mendelian Genetics

Parent 1: TT /Tall

Parent 2: tt / Short

Possibility 1: Tt /Tall

All of the offspring will have the genotype of Tt and a phenotype of Tall

A1:t

A2: t

A1:T

A2:T

A1:T

A1:t

A2:T

A1:t

A2:T

A1:t

A2:T

A2: t

Possibility 2: Tt /Tall

Possibility 3: Tt /Tall

Possibility 4: Tt /Tall

Mendelian Genetics

Parent 1: Tt /Tall

Parent 2: Tt / Tall

Possibility 1: TT /Tall

25% of the offspring will have the genotype of TT (homozygous dominant); 50% off the offspring will have the genotype of Tt (heterozygous); 25% of the offspring will have the genotype tt; 75% of the offspring will be tall; 25% will be short (phenotype)

A1:T

A2: t

A1:T

A2:t

A1:T

A1:T

A2:t

A1:T

A2:t

A1:T

A2:t

A2: t

Possibility 2: Tt /Tall

Possibility 3: Tt /Tall

Possibility 4: tt /Short

Mendelian Genetics

Review from Friday (this is not in your slides)

1. 93.1% of the students in our class do NOT have a cleft chin, but having a cleft chin is a DOMINANT trait. What does this mean?

2. Everyone says you look so much like your uncle! Explain why this statement is misleading.

3. Both of your parents can taste the PTC test strip. However, you can’t! Explain how this can happen in terms of genotypes and phenotypes.

When conducting a cross, one way of showing the potential combinations of parental alleles in the offspring is to align the alleles in a grid called a Punnett square.

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Used to show the genotypic and phenotypic ratios for offspring.

PARENT 1

PARENT 2

Mendelian Genetics

Example: Predict the phenotypic and genotypic ratios of the offspring given the parent genotypes below:

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Parent 1: Widow’s Peak (WW)

Parent 2: No Widow’s Peak (ww)

PARENT 1

PARENT 2

W

W

w

w

Mendelian Genetics

Genotypic Results:

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PARENT 1

PARENT 2

W

W

w

w

Mendelian Genetics

Phenotypic Results:

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PARENT 1

PARENT 2

W

W

w

w

Mendelian Genetics

Example: Predict the phenotypic and genotypic ratios of the offspring given the parent genotypes below:

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Parent 1: (Gg) Green seed color

Parent 2: (gg) Yellow seed color

PARENT 1

PARENT 2

Mendelian Genetics

Genotypic Results:

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PARENT 1

PARENT 2

Mendelian Genetics

Phenotypic Results:

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PARENT 1

PARENT 2

Mendelian Genetics

Mendelian Genetics

Unit 8: Heredity

Part III: Complex, Non-Mendelian Genetics

Book pgs. 188-201

Objectives: H.B.4C.2 Analyze data on the variation of traits among individual organisms within a population to explain the patterns in the data in the context of transmission of genetic information.

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Genetic Diversity in the Classroom

If your earlobes are attached, click yes; If not, click no.

If you have dimples, click yes; If not, click no.

If you are right-handed, click yes. If not, click no.

If you have freckles, click yes; If not, click no.

If you have naturally curly hair, click yes. If not, click no.

If you have a cleft chin, click yes; If not, click no.

If you cross your left thumb over your right, click yes. If not, click no.

If you have a widow’s peak, click yes; If not, click no.

If you can taste the PTC test strip, click yes; if not, click no

If you can roll your tongue, click yes; if not, click no

Many inherited traits result from modes of inheritance that differ from a strict dominant and recessive pattern. Phenotypes can result from alleles with a range of dominance; from the combined effects of more than one gene, or from genes that have more than two alleles within a population.

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Scientists study the patterns of trait (phenotypic) variation within families and populations in order to determine how genes are inherited.

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Non-Mendelian Genetics

Codominance is a form of inheritance wherein the alleles of a gene pair in a heterozygote are fully expressed.

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As a result, the phenotype of the offspring is a combination of the phenotype of the parents. Thus, the trait is neither dominant nor recessive.

Non-Mendelian Genetics

Incomplete dominance is when a dominant allele, or form of a gene, does not completely mask the effects of a recessive allele, and the organism's resulting physical appearance shows a blending of both alleles.

Non-Mendelian Genetics

Sex-linked traits are the result of genes that are carried on sex chromosomes.

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For example, in humans and most other mammals the X and Y chromosomes determine the sex of the organism.

• Sex chromosomes in females consist of two X chromosomes.
• Sex chromosomes in males consist of one X chromosome and one Y chromosome.
• During meiosis I, when chromosome pairs separate, each gamete from the female parent receives an X chromosome, but the gametes from the male parent can either receive an X chromosome or a Y chromosome.

Non-Mendelian Genetics

A Punnett square for the cross shows that there is an equal chance of offspring being male (XY) or female (XX).

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PARENT 1

PARENT 2

X

X

X

Y

Non-Mendelian Genetics

In humans, the Y chromosome carries very few genes; the X chromosome contains a number of genes that affect many traits. Genes on sex chromosomes are called sex-linked genes.

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Sex-linked genes are expressed differently from an autosomal gene. If a gene is on the X chromosome (X-linked),

• female offspring will inherit the gene as they do all other chromosomes (X from the father and X from the mother). The principles of dominance will apply.
• Male offspring will inherit the gene on their X chromosome, but not on the Y chromosome.
• Since males have one X chromosome, they can express the allele whether it is dominant or recessive; there is no second allele to mask the effects of the other allele.

Non-Mendelian Genetics

For example, the trait for color blindness is located on the X chromosome:

• X chromosomes carrying a gene for normal vision can be coded X^C
• X chromosomes carrying a gene for color-blindness can be coded X^c
• Y chromosomes (that lack this gene) can be coded Y
• Only offspring that have the X^C gene will have normal vision.

MALE PARENT 1

REMALE PARENT 2

X^C

Y

X^C

X^c

Non-Mendelian Genetics

Non-Mendelian Genetics

Hemophilia is a disease caused by a sex-linked gene.

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A female can express the sex-linked recessive gene only if it is present on both copies of the X chromosome.

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MALE PARENT 1

REMALE PARENT 2

X^h

Y

X^H

X^H

Non-Mendelian Genetics

Multiple alleles can exist for a particular trait even though only two alleles are inherited.

• For example, three alleles exist for blood type (A, B, and O), which result in four different blood groups.

Non-Mendelian Genetics

Blood Typing Alleles:

• IA and IB are codominant
• The third allele, i, is recessive

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Blood typing genotypes and phenotypes:

• ii yields blood type O
• IA and IB yields types AB
• IA and IAi yields type A
• IBIB and IBi yields type B

Non-Mendelian Genetics

Polygenic traits are traits that are controlled by two or more genes. These traits often show a great variety of phenotypes, e.g. skin color.

Non-Mendelian Genetics

Non-Mendelian Genetics

Assignment: Complete Complex, Non-Mendelian Genetics Practice

You may write all your answers down on the paper first so that you don’t lose any data; but please fill in all final answers on the Google Form posted on Google Classroom!

Baby Bunny Genetics

Unit 8: Heredity

Part IV: Pedigrees

Objectives: H.B.4C.2 Analyze data on the variation of traits among individual organisms within a population to explain the patterns in the data in the context of transmission of genetic information.

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A pedigree is a chart constructed to show an inheritance pattern (trait, disease, disorder) within a family over multiple generations.

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Each generation is represented by the Roman

numeral. Each individual in each generation is numbered from left to right.

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Squares represent males and circles represent females.

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Through the use of a pedigree chart and key, the genotype and phenotype of the family members and the genetic inheritance patterns (dominant/recessive, sex-linked) of traits can be tracked.

Pedigrees

Pedigrees

The gene for this particular genetic trait does not occur on the sex chromosomes; it

occurs on an autosomal chromosome. This information can be inferred from two facts:

1. Both males and females have the trait.
2. Individual III-7 who is a male did not inherit the trait from his affected mother.He received his only X chromosome from his mother.

This particular gene is a dominant gene because each of the people who have the trait has only one parent who has the trait. If only one parent has the trait and the trait is not sex-linked, then the individuals who have the trait must be heterozygous for the gene

Pedigrees

The gene for this particular trait is autosomal recessive. This information can be inferred because:

• affected children are born to unaffected parents,
• and affected children include both males and females equally.

We can deduce that the parents (individuals 1 and 2) must be heterozygotes as they have both affected and non-affected children. Often, rare recessive alleles will be found mostly in heterozygotes and not in homozygotes.

• Matings between relatives (inbreeding) has a greater risk for producing homozygotes with rare recessive alleles than do matings with non-relatives.

Pedigrees

The gene for this particular trait is sex-linked and recessive. This information can be inferred because only males have the trait.

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This is common in X-linked, recessive traits because females who receive the gene for

the trait on the X chromosome from their fathers also receive an X chromosome from their mothers which hides the expression of the trait.

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The trait skips a generation.

Pedigrees

In generation II, all of the offspring receive an X chromosome from their mother.

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Because the males only receive the X chromosome from their mother, they do not receive the gene carrying the trait.

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Because the females receive an X chromosome from their mother and father, they are heterozygous and do not express the recessive trait, but they are carriers.

Pedigrees

In generation III, the offspring of all of the females from generation II have a 50/50

chance of passing a trait-carrying gene to their children.

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If the males receive the trait-carrying gene, they will express the trait.

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If the females receive the trait-carrying gene, they will again be carriers.

Pedigrees

What type of inheritance does this pedigree show? How do you know?

Independent Practice-Pedigrees

What type of inheritance does this pedigree show? How do you know?

Independent Practice-Pedigrees

What type of inheritance does this pedigree show? How do you know?

Independent Practice-Pedigrees

Independent Practice-Pedigrees